This invention relates to a hydrophilic coating including diamond-like carbon (DLC) provided on (directly or indirectly) a substrate of glass, plastic, or the like, and a method of making the same.
It is often desirable to provide a hydrophilic coating (e.g., anti-fog coating) on a substrate such as an automotive windshield, automotive window, automotive mirror, architectural mirror, bathroom mirror, or the like. Such coatings may reduce the likelihood of water drops deposited on the substrate taking globular shape(s), thereby enabling visibility to be improved. In other words, hydrophilic coatings function to reduce bead-like condensation on substrate surfaces (e.g., on the interior surface of an automotive windshield or window). A hydrophilic coating can reduce the formation of many tiny droplets of liquid, which can scatter light, on a surface (i.e., make condensation on a surface film-wise as opposed to droplet-wise).
Unfortunately, certain hydrophilic coatings are not as durable and/or hard as would otherwise be desired and thus are not efficient from a practical point of view for applications such as automotive windshields and/or windows. Furthermore, conventional hydrophilic coatings often cannot withstand high temperatures without breaking down or being damaged. The ability to withstand high temperatures is useful in applications such as automotive windshields where it may be desirable to anneal and/or bend a coated glass article at high temperature(s) after the coating has been deposited.
In view of the above, it is apparent that there exists a need in the art for (i) a coated article (e.g. coated glass dr plastic substrate) having hydrophilic properties, and a method of making the same, (ii) a hydrophilic coating capable of withstanding high temperatures (e.g., up to 600 degrees C., and/or even up to 700 degrees C. in certain embodiments) without being substantially damaged (e.g., burned/burning) or breaking down, and/or (iii) a protective hydrophilic coating for window and/or mirror substrates that is somewhat resistant to scratching, damage, or the like.
It is a purpose of different embodiments of this invention to fulfill any or all of the above described needs in the art, and/or other needs which will become apparent to the skilled artisan once given the following disclosure.
An object of this invention is to provide a durable coated article that it is less likely to attract or be affected by bead-like liquid condensation. Exemplary applications to which such hydrophilic coating(s) may be applied include, for example without limitation, automotive windshields, automotive backlites (i.e., rear vehicle windows), automotive side windows, architectural windows, mirrors, etc.
Another object of this invention is to provide a hydrophilic coating that can withstand high temperatures (e.g., up to about 600 degrees C., and more preferably up to about 700 degrees C.) without being substantially damaged (e.g., burning).
Another object of this invention is to provide a hydrophilic coating that is chemically inert to strong acids and/or bases, and may even act as a barrier against chemical attacks on the underlying substrate in certain embodiments.
Another object of this invention is to provide a scratch resistant hydrophilic coating for use in conjunction with a coated article.
Another object of this invention is to form or provide a hydrophilic coating by doping diamond-like carbon (DLC) with at least one polar inducing dopant(s) such as, for example, boron (B) and/or nitrogen (N). In certain embodiments, the atomic percentage of the polar inducing dopant(s) (e.g., B and/or N dopants, but not including H dopants that may or may hot be added because H is not a polar inducing dopant) is no greater than about 10%, more preferably no greater than about 5%, and most preferably no greater than about 4%. A polar inducing dopant is a dopant that causes DLC to become more graphitic (e.g., cause more sp2 bonds), as opposed to more tetrahedral (i.e., more sp3 bonds). Polar inducing dopant(s) tend to cause the DLC inclusive layer to be more polar, which in turn increases surface energy and thus provides for a more hydrophilic coating.
Another object of this invention is to provide a coated article, wherein a layer of the coating includes both sp2 and sp3 carbonxe2x80x94carbon bonds and has a wettability W with regard to water of at least about 700 mN/m, more preferably at least about 750 mN/m, and most preferably at least about 800 mN/m. This can also be explained or measured in Joules per unit area (mJ/m2).
Another object of this invention is to provide a coated article, wherein a layer of the coating includes both sp2 and sp3 carbonxe2x80x94carbon bonds and has a surface energy "Ugr"c of at least about 24 mN/m, more preferably at least about 26 mN/m, and most preferably at least about 28 mN/m.
Another object of this invention is to provide a coated article, wherein a DLC inclusive layer of the coating has an initial (i.e. prior to being exposed to environmental tests, rubbing tests, acid tests, UV tests, or the like) water contact angle xcex8 of no greater than about 10 degrees, more preferably no greater than about 8 degrees, even more preferably no greater than about 6 degrees, and most preferably no greater than about 4 degrees. The article""s initial contact angle xcex8 may be as low as 1-3 degrees in certain embodiments. In certain embodiments the article""s contact angle may increase over time upon exposure to environmental elements (as graphitic sp2 Cxe2x80x94C bonds wear off) while in other embodiments the article""s contact angle may decrease over time upon such exposure.
Another object of this invention is to provide a hydrophilic DLC inclusive layer for coating a substrate. In at least one portion of the layer no more than about 70% of the bonds in that portion of the layer are of the sp3 type, and more preferably no more than about 60% of the bonds are of the sp3 type. A substantial portion of the remainder of the bonds may be of the graphitic or sp2 type. The bonds in the layer may include, for example, carbonxe2x80x94carbon (Cxe2x80x94C) bonds, carbon-nitrogen (Cxe2x80x94N) bonds, carbon-boron (Cxe2x80x94B) bonds, and/or carbon-hydrogen (Cxe2x80x94H) bonds. The sp3 type bonds (e.g., Cxe2x80x94C bonds) function to increase the hardness and scratch resistance of the coating, while the graphitic sp2 type bonds (e.g., Cxe2x80x94C, Cxe2x80x94N and/or Cxe2x80x94B bonds) cause the coating to be more hydrophilic and have a lower contact angle.
Another object of this invention is to provide a coating which can make accumulated condensation form in a more film-wise manner; as opposed to a droplet-wise manner.
Still another object of this invention is to form amine (NH2) functional groups near the surface of a hydrophobic coating or layer so as to enhance hydrophilicity.
Yet another object of this invention is to fulfill any or all of the above listed objects and/or needs.
Generally speaking, this invention fulfills any or all of the above described needs or objects by providing a method of making a coated article comprising the steps of:
providing a substrate; and
depositing a hydrophilic layer including sp carbonxe2x80x94carbon bonds on the substrate in a manner such that the hydrophilic layer has an initial contact angle xcex8 with a drop of water thereon of no greater than about 10 degrees.
This invention further fulfills any or all of the above described needs and/or objects by providing a coated glass article comprising:
a glass substrate;
a hydrophilic layer including diamond-like carbon (DLC) with sp3 carbonxe2x80x94carbon bonds provided on said glass substrate; and
wherein said hydrophilic layer includes at least one dopant therein so as to cause the layer to have an initial contact angle xcex8 with a sessile drop of water thereon of no greater than about 10 degrees.
This invention further fulfills any or all of the above described needs and/or objects by providing a coated article comprising:
a substrate (e.g., glass or plastic);
a hydrophilic coating or layer including diamond-like carbon (DLC) provided on said substrate; and
wherein said hydrophilic coating or layer has an average hardness of at least about 10 GPa and has an initial contact angle xcex8 with a drop (e.g., sessile drop) of water thereon of no greater than about 10 degrees.
This invention further fulfills any or all of the above described needs and/or objects by providing a coated article comprising:
a substrate; and
a layer comprising amorphous diamond-like carbon on said substrate, said layer having a surface energy "Ugr"c of at least about 26 mN/m.
This invention still further fulfills any or all of the above described needs and/or objects by providing a coated article comprising:
a substrate; and
a layer comprising amorphous diamond-like carbon on said substrate, said layer having a contact angle xcex8 with a drop of water thereon of no greater than about 10 degrees.